Add force once when object is created

I thought that this would add force once as soon as the object was created, but what happens is that the object just falls to the ground. Am I not doing this right?

 using UnityEngine;
 using System.Collections;
 
 [RequireComponent(typeof(Rigidbody2D))]
 public class Bullet : MonoBehaviour {
 
     public int damageAmount;
     public float speed;
     public float timeToLive = 0;
 
     // Use this for initialization
     void Awake () {
         rigidbody2D.AddForce(transform.forward * speed, ForceMode2D.Impulse);
         Destroy(gameObject, timeToLive);
     }
 }